Low-Load Efficiency
It is as important to look at efficiency at the very low end of the supply's potential, and this is because most PCs spend a large portion of their time idling. Right now, my personal PC, on which I am writing, is pulling 36W at the wall!
Top-notch efficiency is harder to achieve in this arena for purely electrical reasons. Even so, the Fractal does a very solid job at all tested wattages. The bonus is the fan doesn't switch on at any of the measured points.